1. Field of the Invention
The present invention relates to a projecting apparatus and a projecting and displaying apparatus which synthesize images formed on a plurality of image forming devices, such as liquid crystal cells, to project and display the synthesized image on a projection surface such as a screen.
2. Description of the Related Art
A liquid crystal projecting apparatus is known which synthesizes images formed on a plurality of liquid crystal cells to project and display the synthesized image on a projection surface such as a screen.
FIG. 6 is a diagram showing the configuration of a conventional liquid crystal projecting apparatus. FIG. 7 is a diagram illustrating that on-axis chromatic aberration may occur with a conventional liquid crystal projecting apparatus. FIG. 8 is a diagram illustrating that magnification chromatic aberration may occur with the conventional liquid crystal projecting apparatus.
As shown in FIG. 6, in this liquid crystal projecting apparatus, a white light source 100 emits white light w. Then, an illuminating optical system 101 and a polarizing optical system 102 adjust the form of a luminous flux and the state of polarization.
An interference filter 103 then separates the white light w for which the shape of the luminous flux and the state of polarization have been adjusted, into lights R, G, B in three respective wavelength areas corresponding to red, green, and blue. The red, green, and blue lights R, G, and B are incident on first prisms 104a to 104c to illuminate liquid crystal cells 105a to 105c arranged opposite the first prisms 104a to 104c. 
When the liquid crystal cells 105a to 105c are illuminated with the lights R, G, and B, images corresponding to the lights R, G, and B are displayed on the liquid crystal cells 105a to 105c, respectively. The images displayed on the liquid crystal cells 105a to 105c pass through the first prisms 104a to 104c, respectively. A second prism 106 then superimposes the images on one another. The resulting image is projected and displayed by a projection lens 107 on a projection surface 108 such as a screen.
However, with a liquid crystal projecting apparatus configured as described above, when the lights R, G, and B pass through the projection lens 107, a difference in wavelength between the lights may cause on-axis chromatic aberration or magnification chromatic aberration, as shown in FIGS. 7 and 9. As a result, the image projected on the projection surface 108 may appear blurred.
Thus, according to the prior art, the projection lens 107 is composed of a plurality of lenses and the shapes, materials, and arrangement of the lenses are improved so as to correct the on-axis chromatic aberration or the magnification chromatic aberration.
However, the projection lens 107 configured as described above is disadvantageous in that for example, the design is complex, is large in size, has a large number of constituent lenses, has a low degree of freedom in selecting the materials of the lenses, and is heavy. This contributes to increasing the size, weight, and cost of the whole apparatus.
Thus, a liquid crystal projecting apparatus has been disclosed in which the spacing between each of the liquid crystal cells and the second prism varies (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-5098). According to this liquid crystal projecting apparatus, even with a projection lens not having a function for correcting chromatic aberration, an image on the projection surface can be prevented from undergoing chromatic aberration by arranging the liquid crystal cells so that the optical distances of each type of light between the liquid crystal cells and the projection lens are equal.
However, magnification chromatic aberration, which may occur in the image on the projection surface, cannot be corrected even by arranging the liquid crystal cells as previously described.